Various kinds of sequentially controlled machines, such as transfer machines, presses, processing machines, feeders, loaders, conveyer systems, etc, generally have a number of actuators sequentially operated so as to perform a sequential operation of the machine, a number of sensors for detecting actions of elements actuated by the actuators, a control system for sequentially controlling the actuators according to signals from the sensors, and a control unit including alarm lamps for alarming i.e., signalling abnormal operations or operational failures, and control buttons or switches for manually operating the actuators for removing operational failures caused in the machine.
Such a sequentially controlled machine often encounters not only troubles of various components leading to malfunction but also various, but insignificant, operational failures, such as slippage of workpieces, the ingress of dust and foreign materials in the sensors and/or the moving elements, etc. which are relatively easily removed. If such removable operational failures occur, the operator speculatively diagnoses the type of operational failure visually indicated by means of alarm lamps and enters or inputs instructions through the control unit to operate the actuators in a certain sequence so as to remove the operational failure, thereby returning or recovering the sequentially controlled apparatus to its normal operational conditions. For example, if a sequential machining apparatus accidentally stops and an alarm lamp indicates that a workpiece clamping member is left inactive against a workpiece, it is usually speculated that the workpiece is not exactly placed in a working position on a work rest. In such a case, the operator attempts to recover the ordinary activity of the workpiece clamping member by removing the workpiece from the work rest and then placing it in the working position on the work rest again.
As to detection of mulfunctions and troubles of various sequentially controlled apparatus or devices, many techniques have been proposed. For example, Japanese Unexamined Utility Model Publication No. 62-75,548 entitled "Residual Working Life Predicting Apparatus", laid open on May 14, 1987, describes a working life precomputing system in which a residual working life of an apparatus is predicted or precomputed and indicated based on a type of trouble striking the apparatus and the probability of occurrence of the type of trouble. Further, Japanese Unexamined Utility Model Publication No. 62-192,853 entitled "Numerical Control Machining Apparatus With Single CRT For Displaying Alarm List", laid open on Dec. 8, 1987, describes a numerical controlled machine in which alarm messages are displayed on a CRT in a desired language.
If an operational failure which is removable happens in the sequentially controlled apparatus or machine, the operator makes an attempt to recover the sequentially controlled machine to its normal operational conditions by actuating some of, or all of, the actuators of the sequentially controlled machine in one or more sequences experimentally adopted. If it is unsuccessful in recovering the sequentially controlled machine in the sequence taken, then the operator actuates other actuators in other sequences, generally different from the previously adopted sequences, so as to recover the sequentially controlled machine to its normal operational conditions or activities.
Because of adoptation of preferable sequences in which recovery operations are executed depending on the experiments and skill of the operator, it is not always that the operator adopts the best sequence of recovery operation for actuating the actuators of the sequentially controlled machine for recovering the sequentially controlled machine to its normal activities. Accordingly, it often takes time to remove operational failures even by a skilled operator and thereby, recovering the sequentially controlled machine to its normal activities. This leads to a lowered efficiency of use of the sequentially controlled machine.